When in use, a shank of a drill bit is clamped within a chuck of a drill. A tip of the drill bit extends beyond the chuck to engage a workpiece into which a hole is being drilled. As the chuck of the drill rotates it imparts a rotary motion to the drill bit, causing the tip of the drill bit to engage the workpiece. Most drill bits are manufactured with cylindrical shanks that are circular in cross-section. Should the resistance provided by the workpiece at the tip of the drill bit exceed the clamping force exerted upon the cylindrical shank, the shank of the drill bit will rotate in the chuck.
In order to prevent rotation of the shank of the drill bit within the chuck, manufacturers such as Viking Drill & Tool Ltd. of St. Paul, Minn., and American Tool Co. Inc. of Willmington, Iowa are manufacturing "tri-shank" drill bits that have three flat areas that assist in avoiding rotation of the shank within the chuck. The number of flat areas need not be limited to three. U.S. Pat. No. 5,466,100 illustrates a drill bit with a hexagonal shank.
The same result can be obtained by using a grinder to create flat areas along the shank of a cylindrical drill bit. For the best results, it is preferred that there be three or more flat areas. Unfortunately, there does not presently exist an apparatus that is particular adapted to permit an average person to grind a shank of a drill bit.